(1) Field of the Invention
The present invention relates to apparatus for transversely cutting a moving sheet, and more particularly refers to a means for cutting a newly formed gypsum board sheet.
(2) Description of the Prior Art
In the production of gypsum board for dry wall use, an aqueous slurry of calcined gypsum containing various conventional additives is deposited between two paper cover sheets and transported on a conveyor until the gypsum slurry becomes almost completely hydrated or set. Conventionally, rotary matching knives are then utilized to cut the moving board transversely into individual boards. The gypsum sheet must be cut when the slurry becomes hard and reaches or almost reaches the point of final set. If knives are used to cut the gypsum sheet while the gypsum is still somewhat soft, a mashing of the material results and the boards must be scrapped.
Recently an apparatus has been developed which utilizes a liquid jet stream produced under extremely high pressure. The jet stream produces a clean, dust-free cut on gypsum board and operates under acceptable noise levels.
The necessity for delaying the conventional cutting of the gypsum board sheet until a final set has substantially been attained is a limiting factor in the speed of the production run. Either extremely long tables or conveyors must be utilized to provide adequate time for setting, or, alternatively, the speed of the line must be reduced to provide sufficient dwell time on the conveyor for setting of the gypsum. It would be desirable to be able to speed up the production line without increasing the length of the conveyor or reducing the speed of the line, while still obtaining a clean transverse cut of the gypsum board.